(1) Field of the Invention
This invention relates generally to dynamoelectric devices, such as electric motors, and more particularly to the stator construction of the device where the stator assembly consists of a stator having a center bore with a plurality of stator poles circumferentially spaced around the center bore. The stator poles have wiring wrapped in windings around the stator poles and the windings have end turns arranged around the stator center bore at axially opposite sides of the stator. The end turns of the windings are laced and manually positioned at opposite ends of the stator to prevent their interference with the rotor assembly in the stator center bore, the motor housing, and/or with the end plates of the motor housing.
(2) Description of the Related Art
In a traditional dynamoelectric device such as a motor, the stator consists of a plurality of stator poles surrounding a rotor. Devices like this are well known in the art, and one is shown generally in FIG. 1. Because such devices are well known, their assembly is only generally discussed here. The stator can be a collection of individual poles as in a segmented stator, or can be formed together as a single unit. As shown in FIG. 1, the stator poles 10, generally, have a xe2x80x9cIxe2x80x9d-shaped cross-section, which creates two channels on opposite sides of a central member 12 or web of the xe2x80x9cIxe2x80x9d-shaped cross section. A length of wire is wrapped around the central member of the xe2x80x9cIxe2x80x9d-shaped cross-section forming wire windings 14 that are partially contained within the channels on opposite sides of the central member 12. Where the wire winding exits one channel at an end of the stator pole 10, crosses over the central member 12, and is redirected to enter the channel on the opposite side of the central member 12, the wire winding creates an end turn 16.
End turns 16 of the wire windings 14 are created at both axial ends of each stator pole. At times windings are formed with the end turns 16 positioned at an axial distance from the opposite ends of the stator pole 10 to provide a smooth transition as they wrap around the end of the stator pole from one channel to the other channel. At this distance from the stator pole, the end turns are grouped and bound together with laces 18. Grouping wire windings 14 with laces 18 prevents the wire windings from interfering with subsequent assembly operations. Generally, materials such as insulated tape or common nylon electrical tie wraps are used as laces 18. After winding, the stator assembly is assembled into a housing 20, a rotor assembly (not shown) is inserted into the stator center bore, and end plates or end bells (not shown) are assembled over the opposite ends of the housing with the rotor shaft supported by bearings in each of the end plates.
There are many methods of motor construction, and the method described herein and shown in FIG. 1, demonstrates one technique where the inside of the housing 20 is fitted to the outer wall of the stator assembly 22. By lacing the end turns 16, the wire windings 14 are prevented from accidentally fouling areas adjacent to the stator poles where the housing 20, rotor assembly (not shown), or end plates (not shown) are installed. As the stator is wound, winding leads 24 are brought from the wire windings 14 around the stator pole for connection outside the stator assembly 22. The winding leads provide current input to the stator poles 10 for the development of electromotive force, and the winding leads 24 provide connection for other electrical switching devices used to regulate current and stator controls. Winding leads 24 must be sized in length for the particular connection to be made outside the stator assembly 22, and the winding leads are often color coded to provide assembly personnel a reference during connection to external devices.
This method of stator construction has many shortcomings. Lacing the end turns 16 and grouping the winding leads 24 is a manually intensive operation, requiring significant manipulation of the wire windings. The manipulation of wire windings 14 causes quality problems. Moreover, the process of generating winding leads 24 and installing winding lead connectors adds assembly time to motor manufacturing.
Misplaced end turns 16 and wire windings 14 can compromise conductivity in the stator assembly 22. As the end turns 16 are manually positioned to clear areas adjacent to the stator poles 10 for the housing 20, the rotor assembly, or end plate installation, grounding of the wire windings can occur. Generally, the wound stator poles 10 are press fit into the housing 20. During this operation, loose winding wires can be accidentally crimped or damaged against the housing 20. End plates (not shown) are often mechanically fastened to the housing 20. Similarly, during this phase of motor construction, loose winding wires can be accidentally crimped or damaged when the end plates are bolted to the housing. When the rotor assembly (not shown) is installed into the stator assembly bore it is critical that the wire windings 14 and end turns 16 do not foul the interface or air gap between the rotor assembly and the stator assembly bore. Often rotor assembly installation is a blind installation, where the end plates obscure viewing of the rotor assembly. It is important that the wire windings and end turns clear the rotor and shaft of the rotor assembly and the bearing assemblies to be fitted thereon.
Protective sealant is applied to the stator assembly 22 and housing to prevent humidity from damaging the wire windings 14 when the motor is de-energized after a period of operation. The protective sealant also provides electrical insulation for the wire windings 14 from other components and debris. This sealant can become cracked if manual manipulation of the end turns 16 and wire windings 14 is needed when the stator assembly 22 is assembled with the housing, the end shields, and the rotor assembly.
Generation of the winding leads 24 is another manual operation required when winding the stator poles. Winding leads 24 must be properly sized in length after winding to allow proper connection to switching devices outside the stator assembly. The winding leads 24 must be specially marked for terminal points, which vary depending upon customer requirements and motor configuration. The length of the winding leads 24 must be sufficient to allow connection to the terminal points, and the ends of the winding leads 24 must be fitted with connectors. These connectors must be specifically configured for the specific terminal point and connector style required for the customer application. Often, winding leads 24 and connectors are color coded to assist assembly personnel in making proper connections. In the prior art mechanical connectors and shrink caps on winding leads 24 have been used to provide connections to terminal points. However, the preparation of winding leads 24 in this manner creates non-standard interfaces for motor construction. This creates inflexibility in the manufacturing lines and slows overall motor production rates.
The winding leads 24 and the connectors attached thereon are frequently used during inspection and testing. Manual connection and disconnection at these points during this phase of the manufacturing process is also labor-intensive. Quality can be compromised as protective sealant is sometimes damaged from the areas of the leads where connection and re-connection was made.
The problems set forth above could be overcome by a device that attaches to the stator assembly 22 of the motor and contains the winding leads 24 and end turns 16 therein, thus eliminating manual lacing of the winding end turns. The device would also have a terminal container to provide uniform connector styles for winding leads. Additionally, the device would be provided with a compartment for housing protectors such as temperature and current overload circuitry.
The shortcomings of the prior art of FIG. 1 are overcome by the present invention which provides a device that contains the end turns of a stator and provides a convenient mechanism for the connection of winding leads of the stator. In general, the invention will be used on the stator assembly such as that shown in FIG. 1, comprising a plurality stator poles, which are wound with wire and arranged in a cylindrical orientation to create an outer diameter adapted for accepting a housing and an inner diameter shaped to accept a rotor assembly (not shown). The wire windings will have end turns positioned at the opposite axial ends of the stator poles. Comprised with the wire windings are the winding leads.
FIG. 4 shows the apparatus of the invention installed on one end of a stator such as that shown in FIG. 1 and described earlier. It should be understood that this particular stator shown and described is only one illustrative environment in which the apparatus of the invention may be employed. The apparatus may be employed with other types of stators. Furthermore, the description of the apparatus to follow is not intended to limit the combinations of configurations of the invention, but to describe the most detailed embodiment. Depending upon style of dynamoelectric device and customer requirements, certain features of the invention can be eliminated without departing from the scope of the invention.
The apparatus of the invention comprises a generally circular shroud that has a xe2x80x9cUxe2x80x9d shaped cross-section. In the preferred embodiment, the shroud is molded of an insulating plastic, although other materials may be used. The cross section is shaped to entirely contain the end turns and winding leads. The shroud is connected to an axial end of the stator assembly by means of stator slot posts, which are press fit into slots created by adjacent stator poles. Molded to the shroud is a terminal container to which the winding leads are attached. Molded into the shroud is a circuitry compartment that houses current and temperature sensing devices. Above the circuitry compartment is a protector cover to hold the temperature and current sensing devices inside the circuitry compartment. Across the protector cover is a clamp that holds the protector cover to the shroud.
The shroud can be fitted to both axially opposite ends of the stator assembly. When a shroud is fitted to both ends of the stator assembly, it is possible one shroud may be constructed without the terminal container, circuitry compartment, or protector cover.